package org.apache.lucene.analysis;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.File;
import java.io.IOException;
import java.io.Reader;
import java.util.Set;

/** Filters LetterTokenizer with LowerCaseFilter and StopFilter. */

public final class StopAnalyzer extends Analyzer {
	private Set stopWords;

	/**
	 * An array containing some common English words that are not usually useful
	 * for searching.
	 */
	public static final String[] ENGLISH_STOP_WORDS = { "a", "an", "and",
			"are", "as", "at", "be", "but", "by", "for", "if", "in", "into",
			"is", "it", "no", "not", "of", "on", "or", "such", "that", "the",
			"their", "then", "there", "these", "they", "this", "to", "was",
			"will", "with" };

	/** Builds an analyzer which removes words in ENGLISH_STOP_WORDS. */
	public StopAnalyzer() {
		stopWords = StopFilter.makeStopSet(ENGLISH_STOP_WORDS);
	}

	/**
	 * Builds an analyzer with the stop words from the given set.
	 */
	public StopAnalyzer(Set stopWords) {
		this.stopWords = stopWords;
	}

	/** Builds an analyzer which removes words in the provided array. */
	public StopAnalyzer(String[] stopWords) {
		this.stopWords = StopFilter.makeStopSet(stopWords);
	}

	/**
	 * Builds an analyzer with the stop words from the given file.
	 * 
	 * @see WordlistLoader#getWordSet(File)
	 */
	public StopAnalyzer(File stopwordsFile) throws IOException {
		stopWords = WordlistLoader.getWordSet(stopwordsFile);
	}

	/**
	 * Builds an analyzer with the stop words from the given reader.
	 * 
	 * @see WordlistLoader#getWordSet(Reader)
	 */
	public StopAnalyzer(Reader stopwords) throws IOException {
		stopWords = WordlistLoader.getWordSet(stopwords);
	}

	/** Filters LowerCaseTokenizer with StopFilter. */
	public TokenStream tokenStream(String fieldName, Reader reader) {
		return new StopFilter(new LowerCaseTokenizer(reader), stopWords);
	}

	/** Filters LowerCaseTokenizer with StopFilter. */
	private class SavedStreams {
		Tokenizer source;
		TokenStream result;
	};

	public TokenStream reusableTokenStream(String fieldName, Reader reader)
			throws IOException {
		SavedStreams streams = (SavedStreams) getPreviousTokenStream();
		if (streams == null) {
			streams = new SavedStreams();
			streams.source = new LowerCaseTokenizer(reader);
			streams.result = new StopFilter(streams.source, stopWords);
			setPreviousTokenStream(streams);
		} else
			streams.source.reset(reader);
		return streams.result;
	}
}
